This invention relates to a bi-metallic snap disk thermostat having an improved bi-metallic disk mounting arrangement to improve the thermal responsiveness of the thermostat operation. This is accomplished by isolating the bi-metal disk from the low thermal conductivity polymeric switch housing. In conventional prior constructions, the bi-metal disk was mounted in contact with the polymeric switch housing. The improvement of the present invention is accomplished by totally enclosing the bi-metal disk in a high thermal conductivity metallic platform.